Energy Sources in Stars (§10.3)
Energy Sources in Stars (§10.3)
Energy Sources in Stars (§10.3)
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<strong>Energy</strong> <strong>Sources</strong> <strong>in</strong> <strong>Stars</strong><strong>Energy</strong> Source #3:Nuclear <strong>Energy</strong>The “lost” mass is converted <strong>in</strong>to energy accord<strong>in</strong>g to E<strong>in</strong>ste<strong>in</strong>’sequation for the rest energy of matter: E = mc 2 (E energy, mmass, c speed light)Example:Suppose that Sun was orig<strong>in</strong>ally 100% H and only 10% of that wasavailable for fusion. Thus…M H available = 0.1 M sunΔM H destroyed through fusion = 0.1 M sun x 0.007total nuclear energy available E tot = (7 x 10 -4 M sun )c 2 ~ 1.3 x 10 44Sun’s s total lifetime energy output = 6 x 10 43 JE tot ~ 2 x the total energy Sun has emitted!!→ Sun could sh<strong>in</strong>e for at least another 5 x 10 9 yr at its current lum<strong>in</strong>osityHence t nuclear for Sun ~ 10 10 yrs44 J
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